147
Journal of Organometallic Chemistry, 384 (1990) 147-153
Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands
JOM
20519
Ferrocene compounds
XVII *. Synthesis of some ferrocenyl carbinols, ethers,
and ureas
S. KovaC
Faculty of Food Technologv, University of Osijek, Yu-54000 Osijek (Yugoslavia)
and V. Rapid * *
Faculty of Food Technology and Biotechnology, University of Zagreb, Yu-41000 Zagreb (Yugoslavia)
(Received July lOth, 1989)
Abstract
Reduction of several aroylferrocenes
(1) with sodium borohydride in methanol
has given 20-64%
yields of ar-arylferrocenemethanols
(2). Reaction of ferrocene
with benzaldehyde in sulphuric acid at - 10 o C gave cu-phenylferrocenemethanol
(2b) (29%) and bis[phenyl(ferrocenyl)methyl]
ether (3a) (35%), and similar reaction
with tolualdehyde gave the corresponding carbinol 2e (21%) and the sym-ether 3b
(42%). Condensations
of the carbinols with methyl isocyanate gave N-[aryl(ferrocenyl)methyl]-N,
N ‘-dimethylureas
(4) in 22-61%
yields.
In continuation of our work on metallocenes [l] and carbamates [2], we decided
to prepare some ferrocene-containing
carbamates, starting from ferrocenylcarbinols.
By use of the procedures described by Cais and Eisenstadt [3] and by Roberts et
al. 141 we have prepared l-ferrocenylethanol
(2a) and several a-arylferrocenemethanols (2b-2g) by reduction of acetylferrocene
and the corresponding aroylferrocenes (1) [5], respectively, with sodium borohydride in methanol (yields 20-64%,
see Table 1).
A potentially simpler route to ferrocenylcarbinols
is offered by direct hydroxyalkylation of ferrocene with carbonyl compounds, in strongly acidic medium [lo], but
although we followed exactly the procedure used for the synthesis of a-phenylferrocenemethanol (2b) [lo], in addition to this carbinol (29%) we isolated 35% of the
* For Part XVI see ref. 1.
* * Adressee for correspondence.
0022-328X/90/$03.50
0 1990 Elsevier Sequoia S.A.
P-CH&K
p-CH,OC,H,
z-furyi
2e
2f
2g =
-- --- ~~___-----._-._
o Anal., found: C. 68.15;
dXjCgH4
2d
_.
--
.
._
c&d.:
_ -
<“. 67.70;
II. S.20%.
(Lm)
C131)
_
6.49
4.37
0d)
(2.d)
--
6.85
7.33
7.17
72-14
,3]
1.32
(4.m)
(4,m)
7.46
(2-m)
7.31
-.
H(3)
100 MHz)
O,m)
_~
H(6)
protons
(S. D,CCOCD,,
(2)
[3,81
191
_
1.22
(km)
I71
_
[El
7.53
-
Aromatic
----____
H(2)
‘H NMR
81-82
[61
H, 5.05. C‘,,Ht,FeO,
66-68
69-70
7o-72
58-60
4
p-ClC,
2c
H
78-8o
C,HS
2b
78-79
(“C)
[lit.]
(“C)
70-72
m.p.
for C,,H,FeCH(R)OH
m.p.
data
CH,
and spectral
2a
constants
R
1
Compound
Physical
Table
_
..
.
H(5)
i1.m)
--..-.
7.60
7.00
_
7.31
_.
H(4)
(4.m)
(Is)
(1.d)
5.65
(1.a)
5.51
(9,m)
(km)
4.30
(km)
4.07
(4,m)
3.91
5.34
4.08
5.51
(4,m)
(1,s)
4.09
5.57
(1.d)
5.68
4.10
(1.d)
C.5.s)
(1.m)
4.27
(1,m)
4.53
4.17
(5s)
-
.___..- ~__~~
(1.m)
(3,s)
4.21
4.01
(5.x)
.4.09
(3.~1
3.76
I1.S)
(3s)
2.37
4.28
4.17
2.30
-
~
(3.d)
1.40
CH,
(5,s)
4.13
(Lm)
4.35
4.30
(1,d)
3.55
OH
(5,s)
(5s)
4.22
4.15
ring
(4.m)
4.11
unsuhst
ring
subst.
(l,m)
protons
Ferrocene
4.57
CHO
(I,m)
_____--.
---
3350br
3480s
3452s
35705
3540s
3450s
3220br
u(OH)
IR (cm-
12lOw
1223m
1220m
1230m
1215m
1240m
122ow
1223m
1240m
v(C-0)
II KBr)
149
I
RCHO
4
R = p-CIijO$HL
+ H2S04
Fc-CH-R
bH
2b,e
-
H+
-H20
R = C6H5,
+
R-CciH
+ FcH
rtl_‘,
kCH3C6HL
Fc-6H
k
1
*
2
x
FcCH-O-CHFc
k
k
m
Scheme 1
corresponding
sym-ether (3a). The reaction of ferrocene with tolualdehyde
in
concentrated sulphuric acid likewise gave 42% of ether 3b and 21% of carbinol 2e.
Attempts to condense ferrocene with anisaldehyde,
p-nitrobenzaldehyde,
and
terephthalaldehyde
under similar conditions were unsuccessful.
The results can be understood in terms of the exceptional ease with which
hydroxyl group is eliminated from the initially formed carbinols (2), to give the
stable a-ferrocenylcarbonium
ions (I) which then undergo the nucleophilic attack by
another molecule of carbinol to give sym-ethers (3) (Scheme 1). When tolualdehyde
is used, the intermediate I is further stabilized by the p-methyl group, and so ether
3b is the major product. In the case of the resonance-stabilized
protonated
anisaldehyde
the positive charge is dispersed over the conjugated
framework,
lowering its reactivity towards ferrocene. The stabilities of protonated
p-nitrobenzaldehyde and terephthalaldehyde
are reduced by the electron-withdrawing
effects
of the p-substituents so that there is again no reaction with ferrocene. We concluded
that the reaction of ferrocene with aromatic aldehydes cannot be regarded as a
general method for the preparation of the cu-arylferrocenemethanols.
Lorkowski and co-workers [l l] have described the reactions of ferrocenemethanol
and 1-ferrocenylethanol
with methyl, aryl, and cyclohexyl isocyanates. They showed
that reactions of equimolar amounts of aliphatic isocyanates with ferrocenylcarbinols in toluene, at room or higher temperatures gave the expected ferrocenylmethyl carbamates as the major products. In the reactions of aryl isocyanates with
the same carbinols they postulated formation of the N-(ferrocenylmethyl)anilines
as
intermediates, which are then converted into N, N-bis(ferrocenylmethyl)anilines
and
a small amount of N, N ‘-diaryl-N-ferrocenylmethylureas.
Our attempts to prepare analogous carbamates from carbinols 2a-2g and methyl
isocyanate in toluene were unsuccessful. Reactions of equimolar amounts of the
reactants, with or without triethylamine
present at room temperature
or upon
heating gave only the starting materials and some unidentified
decomposition
products. Reactions of carbinols 2a-2g with an excess of the methyl isocyanate in
boiling toluene gave only the urea derivatives 4, in yields of 21-61%. (TLC of the
reaction mixtures showed no other products.)
This course of reaction may involve one of the possible pathways depicted in
Scheme 2. Formation either of the previosly mentioned secondary and tertiary
amines, or of ureas 4, appears to be possible only via the ol-ferrocenylcarbonium
FcCH(OH)R
+
CH3NC0
e
FcCHROOCNHCH~
F
y?
FcCH+
G@s
7
d---Y
Fc CH ii-C-0
+
CiOCNH
CH3
IV
a
-co2
R
Fc&HNHCH3
CH3NCO
D
7
FcCH
1
III
Scheme
b
+ -OOCNHCH3
11
J
=
I
2
b,lCCNHCH3
i
-co2
CH3
2
ions II, but such species can be formed from ferrocenylcarbinols
only in the
presence of an acid [12]. Since the reactions of carbinols with methyl isocyanate
were performed in neat toluene (possible traces of water or acidic impurities would
be removed by reaction with the excess of reagent) we suggest that there is initial
formation of carbamate I. Like the analogous acetate [g], the ester I could be
heterolytically
cleaved in an uncatalyzed reaction to give carbonium ion II and
carbamate anion. This anion would undergo decarboxylation
and the amine ion
formed react with II to give the secondary amine III, which would finally give urea
4 (route n). In an alternative pathway h, II could react with isocyanate to give IV,
which could add carbamate anion to give the mixed anhydride V, which could then
be decarboxylated
to give urea 4.
In a control study we examined the reaction of ferrocenylmethanol
with methyl
isocyanate under the condition used by Lorkowski [ll]. and also with heating, but
we isolated only the expected ferrocenylmethyl
N-methylcarbamate.
We conclude that the stability of a-ferrocenylcarbonium
ions, further enhanced
by presence of a-aryl-substituents,
makes possible the cleavage of the initially
formed carbamates, so that the reaction is driven towards formation of ureas.
The structures of the ureas prepared are unambiguously
confirmed by their
spectra. There are strong IR bands at 33753315 attributable to v(N- H). bands at
2970-2915 corresponding
to Y(C-H) for the methyl groups, and strong bands at
1680-1620 cm~-’ attributable to v(C=O). In the ‘H NMR spectra the ferrocene and
aromatic protons are found at their usual positions. the methine protons give
singlets at 6.83-6.69 (5.77q for 4a), the amide protons at 6.13--5.71 (b), and the
IV-methyl protons at 2.95-2.66 ppm (s or d).
Experimental
The m.p.‘s were determined with a Biichi apparatus and are uncorrected.
spectra were recorded as KBr pellets with a Yerkin-Elmer
257 Grating
Spectrophotometer.
The ‘H NMR spectra were recorded on a Varian
spectrometer with tetramethylsilane
as internal standard.
All experiments were performed under argon.
Acetylferrocene
and aroylferrocenes (la-lf)
were prepared by acylation
cene [5]. l-Ferrocenylethanol
(2a) and cY-arylferrocenemethanols
(2b-2g)
The IR
Infrared
EM 360
of ferrowere ob-
151
mined by reduction
[3,4] (Table 1).
of acetylferrocene
(la-If)
and aroylferrocenes
with NaBH,
Reaction of ferrocene with benzaldehyde and p-toiualdehyde
The aldehyde (5 mmol) was added dropwise to a mixture of 16 ml of H,SO,
cont. and 2 ml of water cooled to - 8” C. Ferrocene (930 mg, 5 mmol) was added in
several portions with stirring. After further vigorous stirring for 1 min, 20 ml of ice
water was added dropwise. The resulting viscous deep red solution was added to ca,
300 ml of cold water. The yellow suspension obtained was extracted with diethyl
ether, and the extracts were washed with 10% aqueous NaHCO, then with water,
and dried over MgSO,. After evaporation of solvent, the oily residue was chromatographed on silica-gel: light petroleum eluted the unreacted ferrocene, and gradual
increase in the diethyl ether content of the eluant to 30% gave the fractions
containing bis[aryl(ferrocenyl)methyl]
ether (35% 3a, Ar = phenyl; 42% 3b, Ar = ptolyl) and ar-arylferrocenemethanol
(29% 2b, 21% 2g), respectively *. 3a, m.p.
51-54°C
(lit. [7] 52-56” C). 3b, m.p. 129-130°C
(Analysis. Found: C, 72.97; H,
5.92. C,,H,,Fe,O
calcd.: C, 72.75; H, 5.77%) ‘H NMR (6, CDCl,): 7.23 (8H, m,
C,H,), 4.99 (2H, s, CHO), 4.01 (lOH, s, unsubst. ferrocene ring), 3.89 (8H, m, subst.
ferrocene ring), and 2.38 ppm (6H, s, CH,). IR (KBr): Y(C=C) IS15 m, Y(C-O-C)
1085 s cm-‘.
N-[Aryl(ferrocenyl)methy[j-N,N
‘-dimethylureas (4a-4e)
A solution of 1 mm01 of the appropriate carbinol 2 and 2-3 mmol of methyl
isocyanate in 3-9 ml of toluene was refluxed for between 5 min and 2 hours, the
progress of the reaction being monitored
by thin layer chromatography.
The
mixture was set aside for 24 h then either the crystals, which had separated were
filtered off (4b, 4c) or the reaction mixture was evaporated to dryness. In the latter
case the resulting resinous residue was recrystallized from hexane to give the pale
Table 2
Yields, analyses and melting points of the compounds
Com-
R
Formula
pound
4a
4b
4c
4d
4e
CH,
C,HS
p-CIC,H,
m-CH&H,
p-CH30C6H4
Cdf20FeN20
C&LFcN#
C,H,,CIFeN,O
C2,Hz,FeN$
CXHXF~N@Z
68-69
178-180
184-185
150-151
184-186
R
CH,
I
I
C,,H,Fe-CH-N-CONHCH,
Yield
Analysis (found (calcd.) (%))
(X)
C
22
22
61
H
N
59.88
6.65
9.22
(60.02)
(6.72)
(9.33)
Cl
-
66.36
5.85
7.58
(66.31)
(6.12)
5.45
(7.73)
6.87
9.04
(5.34)
(7.06)
(8.94)
60.71
(60.55)
-
34
67.28
6.73
7.59
-
39
(67.03)
64.45
(6.43)
6.18
(6.16)
(7.44)
6.93
(7.14)
-
(64.30)
* Yields of products are based on ferrocene used up.
(4)
I
R
CH,
”
7.41
_
(2.m)
7.15
1.35
(2,m)
,,.
_
6.80
(2,m)
1.47
(2,m)
.
are presented
(4,m)
-
1.25
(km)
_
H(5)
5.77
(1Jl)
6.13
(Is)
6.83
(1,s)
6.81
(1,s)
6.69
(1,s)
4.34
(2,m)
4.23
(2.m)
4.34
(2,m)
4.29
(2,m)
4.06
4.23
t2,m)
4.06
(2.m)
4.18
(2.m)
4.26
(2,m)
4.28
(5,s)
4.19
(5.~)
4.31
(5,s)
4.31
(5,s)
4.19
((5s)
ring
unsubst
Ferrocene protons
substituted
ring
t 1-b) t4.m)
6.13
(1-b)
5.11
(Lb)
5.91
(Lb)
5.81
0.b)
5.71
NH
(3s)
2.80
(3,s)
2.19
(3s)
(3,d)
2.92
(34
2.91
(3,s)
2.80
(3.d)
(3,s)
2.66
2.95
(3,s)
2.68
NCH,
2.82
(3.d)
2.80
NHCH,
- -.--.- “_..I_._.-_.“-.l- ---“.-~l .~~-~. .__-__.___
in the Table 2.
1.06
_
H(4)
H(6)
H(3)
I
-CH
1
100 MHz)
(4)
Aromatic protons
‘H NMR spectra (6, D,CCOCD,.
---__
-._
” The structures of the ureas prepared
4e
4d
4c
4b
4a
Compound
The spectral data of C’OHPFe-CH-~-CONHCH,
Table 3
(3s)
______
2.40
(3,s)
3.77
--
(3,d)
~
1.60
OCH,
CCH,
or
’
3375s
3320s
3360s
3330s
331%
v(N-H)
2935m
2960m
2Y20m
2915~
2940~
2970~
v(CH)(CH3)
IR spectra (cm- ‘, KBr)
1625s
1620s
1627s
1620s
1680s
v(C=O)
153
yellow crystals of 4a, 4d and 4e (Tables 2 and 3). When a catalytic amount
triethylamine was present during the reactions similar results were obtained.
of
Acknowledgement
We are indebted to Dr. V. SunjiC and Professor D. Sunko for helpful discussions.
We thank Dr. J. JelenEiC and Mrs. J. BrckoviC for recording the IR spectra, and the
Council for Scientific Research, Socialist Republic of Croatia, Zagreb, Yugoslavia
for partial support through a grant.
References
1 N. FilipoviC- Marinic, V. RapiC, V. Kramer and B. Kralj, J. Organomet.
2
3
4
5
6
7
8
9
10
11
12
Chem., 296 (1985) 405, and
ref. cited therein.
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und E. Reiner, Croat. Chem. Acta, 58 (1985) 87.
M. Cais and A. Eisenstadt, J. Org. Chem., 30 (1965) 1148.
G. Neshvad, R.M.G. Roberts and J. Silver, J. Organomet. Chem., 236 (1982) 237.
R.J. Ranson and R.M.G. Roberts, J. Organomet. Chem., 260 (1984) 307.
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